Infrared spectral properties for α-NaYF4 single crystal of various Er3+doping concentrations

• α-Er: NaYF4 single crystals were grown by Bridgman method.
• The strong ~1.5 μm and ~2.7 μm emissions are observed for Er:NaYF4 crystals.
• The Judd–Ofelt parameters based on absorption spectra are obtained.
• Absorption/emission cross-section spectra by McCumber theory are reported.
• Gain cross-section spectra of ~1.5 µm and ~2.7 µm are studied.

The α-NaYF4 single crystals doped with 0.2 mol%, 0.5 mol%, 1 mol%, 2 mol% and 3 mol% Er3+ ions were fabricated by an improved Bridgman method. The ~1.5 µm and ~2.7 µm emission properties were investigated in detail through the measured absorption and emission spectra. A Judd–Ofelt analysis of Er3+in α-NaYF4 samples is performed. The Judd–Ofelt parameters are obtained (Ω2=2.71×10−20 cm2, Ω4=2.28×10−20 cm2, Ω6=0.84×10−20 cm2) and the radiative lifetimes of Er3+energy levels and the branching ratios of Er3+transitions are calculated. The calculated maximum emission cross section by McCumber theory for ~1.5 µm and ~2.7 µm reached 1.35×10−20 cm2 and 2.2×10−20 cm2, respectively. The gain cross section spectra were calculated based on the absorption and emission cross section spectra. All these spectral properties indicated that this kind of fluoride crystal has potential application as host material for infrared lasers.